The present invention relates to a process for recovering surfactants in an aqueous solution from organic compounds contaminating the solution.
The present invention is particularly useful for recovering surfactants in aqueous waste streams generated by hazardous waste treatment processes. For example, organic compounds such as polychlorinated biphenyls (PCBs) and other phenyl compounds, non-vinyl compounds such as imidazole and pyrrole and other hazardous organic compounds must be removed from equipment contaminated therewith by hazardous waste treatments in accordance with governmental regulations before the equipment may be reused or scrapped. Such contaminated equipment is commonly cleaned by circulating a surfactant-containing (or detergent-containing) aqueous solution therethrough to wash the organic compounds from the contaminated areas and surfaces. Similar applications include the use of surfactants to remove contaminating organic compounds from soils, ashes and other solids. Surfactants employed to remove residual amounts of PCBs and like organic compounds include ethoxylated aromatics such as HYONIC NP-90 acid esters from Henkel Chemical Corporation or polyoxyalkylated fatty acid esters such as ADSEE 799 acid esters from Witco Chemical Co. Other surfactants may include carboxylic acid salts, sulfonic acid salts, sulfuric acid ester salts, phosphoric acid esters, long-chain amines, quaternary ammonium salts, polyoxyethylenated alkylphenols, polyoxyethylenated polyoxypropylene glycols, polyoxyethylenated mercaptans, polyoxyethylenated silicones and alkylpolyglycosides.
After cleaning the equipment, the contaminated surfactant-containing aqueous solutions must then be treated as hazardous wastes before they can be reused or discharged. Undesirably, in the present state of the art, aqueous solutions contaminated with PCBs and the like are treated by coprecipitating or by coadsorbing both the contaminants and the surfactants from the aqueous solutions. Thus, the surfactants are only used on a once through basis, and therefore, additional surfactants must be added to the solutions before they can be reused. Also, the additional volume and weight of the coprecipitates due to the coprecipitated surfactant or the contaminant loaded adsorbents results in additional material costs to remediate the contaminants.
U.S. Pat. No. 4,765,901 to Field discusses a method for purifying waste water wherein phenolic compounds are polymerized by an oxidative technique to form extractable polyphenols while avoiding their precipitation.
U.S. Pat. No. 4,844,745 to Nash et al. discloses a process employing the use of solvents to remove residual PCBs from electrical transformers and the like. Undesirably, this type of process does not separate the PCBs from the solvents, and the solvents must be disposed of as waste streams.